Insect with wings
(though forewings may be partly or entirely stiffened as 'wing-covers'
or 'wing-cases' and not used in flight)

2

1b

Insect without
wings (though some forms may retain vestigial wings resembling
small scales or pads)

32

2a

One pair of wings

3

2b

Two pairs of wings

9

3a

Dorsal surface of the
prothorax extended backwards over the abdomen; hind-legs enlarged and
modified for jumping; insect grasshopper-like in general appearance

Orthoptera

3b

Insect not like this

4

4a

Wings horny or leathery
(stiffened) and not used for flying

5

4b

Wings membranous (flexible)
and used for flying

6

5a

Wings overlapping at
least a little in the centre-line and with obvious veins present

Phasmida

5b

Wings (elytra) meeting
in the centre-line (sometimes fused together) and without veins
(elytra may have longitudinal grooves or striae which should not be
confused with veins)

Coleoptera

6a

Abdomen with one or more long
terminal appendages

7

6b

Abdomen without terminal
appendages

8

7a

Wings with only one
forked vein; antennae relatively long; small insect usually less than
5 mm long

Hemiptera

7b

Wings with many veins; antenae short; alrge insect

Ephemeroptera

8a

Thorax with a pair of
club-shaped structures (halteres) lying just in front of the wings

Strepsiptera

8b

Thorax with a pair of
club-shaped structures (halteres) lying just behind the wings (may
be hidden by body hairs and other structures)

Diptera

(insect with two pairs of wings)

9a

Forewings partly or
entirely horny or leathery and forming stiffened covers for the membranous
hindwings

10

9b

Both pairs of wings membranous
(flexible) and used for flying (though wings sometimes feather-like
rather than membranous or their membranous nature may be obscured by a
dense covering of hairs, scales or waxy powder)

16

10a

Mouth-parts forming a
tube-like 'beak' (rostrum) for piercing and sucking (rostrum usually
folded backwards under the body when not in use)

Hemiptera

10b

Mouth-parts with jaws
(mandibles) for biting and chewing

11

11a

Forewings overlapping at least
a little in the centre-line and usually with many veins present

12

11b

Forewings (elytra) meeting in
the centre-line and without veins (though elytra may have longitudinal
grooves or striae which should not be confused with veins)

14

12a

Hind-legs enlarged and
modified for jumping; insect grasshopper-like in general appearance

Orthoptera

12b

Hind-legs not modified for jumping and usually similar in thickness to the middle-legs; insect not grasshopper-like

13

13a

Prothorax much larger
than the head; cerci nearly always many-segmented and fairly prominent

Dyctioptera

13b

Prothorax and
head of similar size; cerci always unsegmented and very short

Phasmida

14a

Forewings (elytra)
long and covering all or most of the abdomen

Coleoptera

14b

Forewings (elytra) short and leaving much of the abdomen exposed

15

15a

Abdomen with a pair of
terminal pincers or forceps

Dermaptera

15b

Abdomen without
terminal pincers

Coleoptera

16a

Wings very narrow
without veins and fringed with long hairs (feather-like); tarsi 1- or
2-segmented (small slender insect often found in flowers)

Thysanoptera

16b

Wings broader with veins
present; if wings fringed with long hairs then tarsi comprised of more
than 2 segments (though wing veins of some insects may be much
reduced and hardly visible or partly obscured by hairs, scales or waxy
powder)

17

17a

Hindwings noticeably smaller
than forewings

18

17b

Both pairs of wings similar in size or hindwings larger than forewings

26

18a

Wings and much of the body
covered with white waxy powder; tiny insect usually less than 2-3 mm
long

19

18b

No such powdery covering

20

19a

Wings held flat over
the body at rest; mouth-parts forming a tube-like 'beak' (rostrum) for
piercing and sucking (rostrum usually folded backwards under the
body when not in use)

Hemiptera

19b

Wings held roof-wise
over the body at rest; mouth-parts with jaws (mandibles) for biting

Neuroptera

20a

Wings more or less
covered with minute scales; mouth-parts when present forming a coiled
proboscis or 'tongue'

Lepidoptera

20b

Wings usually transparent
(without scales though often hairy); mouth-parts not forming a coiled
proboscis

21

21a

Forewings with many
cross-veins making a network pattern; abdomen with 2 or 3 long thread-like
terminal appendages

Ephemeroptera

21b

Forewings with relatively few
cross-veins; abdomen usually without or with only very short terminal
appendages (cerci)

22

22a

Wings noticeably covered
with hairs; insect moth-like in general appearance

Trichoptera

22b

Wings not noticeably hairy
(though may be fringed with hairs or tiny surface hairs may be seen if
wings examined under a microscope or strong hand-lens)

23

23a

Mouth-parts forming
a tube-like 'beak' (rostrum) for piercing and sucking (rostrum
usually folded backwards under the body when not in use; abdomen
sometimes with tubular outgrowths or cornicles near the hind end)

Hemiptera

23b

Mouth-parts with jaws
(mandibles) for biting and chewing

24

24a

Tarsi 4- or 5-segmented;
hard-bodied insects with abdomen often constricted at its base into a
petiole or 'waist' (except Symphyta)

Hymonoptera

24b

Tarsi 2- or 3-segmented; small
soft-bodied insect

25

25a

Antennae with at
least 12 segments

Psocoptera

25b

Antennae with only
9 segments

Zoraptera

26a

Tarsi 5-segmented

27

26b

Tarsi 3- or 4-segmented

29

27a

Wings noticeably covered
with hairs; insect moth-like in general appearance

Trichoptera

27b

Wings not noticeably
hairy (though tiny hairs may be seen if wings examined under a
microscope or strong hand-lens)

28

28a

Front of head extended
downwards to form a beak-like structure with jaws (mandibles) at its
tip

Abdomen strongly
constricted at its base into a narrow petiole or 'waist'; antennae
often bent into an elbowed shape

Hymenoptera

62b

Abdomen not constricted into a
'waist'; antennae more or less straight

63

63a

Body covered with dense
scales and flattened hairs

Lepidoptera

63b

Body bare or with sparse
bristle-like hairs

64

64a

Mouth-parts forming a tube-like proboscis or rostrum for piercing and/or sucking (often folded backwards under the head when not in use)

65

64b

Mouth-parts with jaws (mandibles) for biting and/or chewing

67

65a

Tarsi usually 5-segmented

Diptera

65b

Tarsi with fewer than
5 segments

66

66a

Proboscis small and
cone shaped (much shorter in length than the head) (small slender
insect often found in flowers)

Thysanoptera

66b

Proboscis or rostrum long
and jointed (nearly always longer than the head) (abdomen sometimes
with tubular outgrowths or cornicles near the hind end)

Hemiptera

67a

Antennae short and often
inconspicuous (at most about the same length as the head)

68

67b

Antennae long and conspicuous
(much longer than the head)

69

68a

Abdomen with 6 segments
or fewer

Collembola

68b

Abdomen with more than 6 segments (usually
8 or more clearly visible)

Larvae of Variuor order

69a

Head narrower than
the body; mandibles very long and protruding forward well in front of
the head (clearly visible from above)

Larvae of Neuroptera

69b

Head as wide or nearly
as wide as the body; mandibles small and not protruding in front of the
head (not visible from above)

Psocoptera

(insect without wings - aquatic)

70a

Mouth-parts with
a tube-like 'beak' or with long stylets for piercing and sucking

71

70b

Mouth-parts with jaws
(mandibles) for biting and/or chewing

72

71a

Mouth-parts forming a
robust tube-like 'beak' (rostrum) folded backwards under the body when
not in use

Hemiptera

71b

Mouth-parts forming a
pair of long and slender stylets extending more or less straight forward
in front of the head between the antennae and about as long or longer than
the latter

Larvae of Neuroptera

72a

Head with a hinged
protrusible grasping organ (or 'mask') bearing large terminal claws
(normally folded beneath the head when not in use)

Nymphs of Odonata

72b

No hinged protrusible 'mask'
beneath the head

74

73a

Abdomen with pairs of
feather-like or flat plate-like lateral appendages on some segments (gill
filaments) and 3 long terminal appendages (paired cerci and a median
filament)

Nymphs of Ephemeroptera

73b

Without these features
combined

74

74a

Abdomen without lateral
appendages but with 2 long terminal appendages (cerci); antennae long and
slender (much longer than the head)

Nymphs of Plecoptera

74b

Without these features
combined

75

75a

Abdomen with pairs of
multi-jointed feather-like lateral appendages on some segments (gill
filaments) and sometimes a single terminal appendage

Larvae of Neuroptera

75b

Abdomen without lateral
appendages (gill filaments) or if such appendages present then always
unjointed

76

76a

Last abdominal segment
with a pair of fleshy appendages each bearing a strong claw; middle- and
hind-legs longer than the width of the thorax; body often enclosed in a
tubular case made from small pebbles or other debris